Mill screen



Patented Sept. 19, 1950 UNITED STATES PATENT OFFICE ltIILL SCREEN I Farrell G. Lively, Cherokee, kla., assignor to Earnest M. Wetmore, Tonkawa, Okla.

Application June 30, 1947, Serial No. 758,018

4 Claims.

This invention relates to feed grinders or ensilage cutters, and more particularly to the screens therefor which cooperate with the rotor in reducing materials to comminuted form.

Screens of this type usually include a transversebar or bar segments, and considerable difficulty is experienced with the binder twine and tough haywhen hay and bundled feed stuff are being reduced. The tough hay and binder twine, particularly when wet, pile up on the bars and choke the passages through the screens. Also, such bars have little cutting effect and cause the feed to be discharged in a ropy condition. The bars when worn or dulled require replacement of the entire screen with a new one, involving needless expense.

Therefore, the principal objects of the present invention are to provide a screen having staggered blades with cutting edges which more effectively cut'wet twine and tough hay and to provide an arrangement of blades which allows the cut material to pass freely through the screen improved elements and arrangements thereof in a screen of this character which is simple, econo-mical to manufacture and eflicient in operation.

In accomplishing these and other objectsof the present invention, I have provided improved details of structure, the preferred form of which is illustrated in the accompanying drawings, wherein:

Fig. 1 is a vertical longitudinal section through a hammer mill provided with a screen embodying the features of the present invention.

Fig. 2 is a perspective view of a screen'embodying the features of the present invention.

Fig. 3 is a partial plan View of the screen particularly illustrating the staggered arrangement of the blades.

Fig; 4 is an enlarged sectional view through the screen taken on the line 44, Fig. 3.

Referring more in detail to the drawings:

1 designates a hammer mill or cutter for reducing hay ensilage and similar crops and which includes a base 2 carrying spaced side walls, one of which is shown at 3, and end walls 5 and 6 to form a casing l. The upper ends of the side walls taper upwardly and inwardly as at 8 and 9, and the upper portion IQ of the end wall S'follows the shape of the side walls. The upper portion ll of the end wall 6 curves toward the portion it but terminates short thereof to provide a discharge opening or outlet l2. Connected to the outlet I2 is a discharge duct l3 throughwhich material is discharged from the casing '7.

Carried between the side walls and extending from the end wall 5 to the end wall 61s a plate l5 Whichcooperates with the curved portion H and a screen member I6 to complete a substantially cylindrical rotor chamber 11.

Journalled in the sides of the casing coaxially of the rotor chamber is a drive shaft l8 carrying a rotor E9 having a plurality of radially extending hammers 29 that pivot freely in one direction on the rotor for cooperating with the screen in reducing material that is fed into the rotor chamber through an inlet 21 indicated by the dotted lines (Fig. 1).

The above described structure, with the exception of the screen, is that of a conventional type grinder which specifically forms no part of the present invention.

The screen l6 includes a frame 22 having arouate side rails 23 and 24 connected by end rails.

25 and 2E. Extending laterally into the space between the arcuate side rails 23 and 24 to a point slightly beyond midway of the median arc of the screen are blades 21. The blades 21 are in the form of triangular shape and may com prise ordinary sickle blades having apertures aligning with apertures in the side rails 23 and M for attachment by rivets or similar fastening devices which permit ready removal of the blades when worn or dulled.

The triangular shape of the blades provides diverging edges 28 and 29 which are sharpened to:

form bevelled cutting edges 39 and 3i. The cutting edges 353 and M of the blades are adapted to lie in alignment with the outer surface 36 of the side rails 23 and 24 of the frame 22 which provide clearance between the cutting blades and the hammers of the rotor. The blades on the respective side rails arev also preferably staggered as shown in Figs. 2 and 3, which arrangement assures proper cutting of the material and leaves ample space for discharge of material into the discharge duct. The triangular shape of the blades and their cutting edges facilitates shredding of the material and prevents balling upof the material and adherence thereof to the blades of the screen. It will be noted on inspection of,

the blades on the opposite side. Thus, both side edges of the blades are effective while the material is being pushed through the passageway by the hammers. The angular position of the cutting edges also cooperates with the hammers in producing a shearing action on the material which assures cutting up of the wet binding twine and tough materials.

The concave screen is supported in the upper portion of the housing by spaced guide members 33 on each of the side walls to provide slots which receive the edges of the side rails 23 and 24, the screen being inserted through a slot 34 formed by the spacing of the end I I of the end wall 5 from the discharge duct. The screen is moved through the guides until the end rail 25 engages the end 35 of the curved plate [5. The screen is held in place by a stop member 36 enclosing the slots through which the screen is inserted.

Operation of an ensilage cutter or hammer mill equipped with a screen constructed and assembled as described is as follows:

Material or other ensilage, such as feed, out corn-stalks and/or grasses in either wet or dry state, is supplied to the rotor chamber of the mill through the conventional feed opening 2|. Upon operation of the drive shaft [8, the rotor is turned in a clockwise direction (Fig. 1) at suflicient speed to circumvolve the material about the rotor chamber and across the screen, whereby centrifugal force acts on the material to hold it while it is acted upon by the hammers and pushed thereby through the tortuous passageway of the screen to be acted upon by the blades. The twine and stringy material are directed against the sharpened edges of the triangular-shaped blades. 21 to assure comminution thereof so that it does not hang up on the blades of the screen.

Since the cutting edges 30 of the blades in the direction of rotation are apt to become dull before the cutting edges on the retractive sides, the screen It may be removed and placed in reverse position so that the cutting edges 3! will be in position to cut and chop the material going through the mill, thus providing a longer lasting screen and obviating numerous replacements of the blades. However, when the blades are worn on both edges, they are readily removable and replaced, thereby obviating the necessity of replacing the entire screen.

It will be apparent from the foregoing that I have provided an improved screen for ensilage cutters or hammer mills which will be of longer life and obviate replacement at frequent intervals, and one which will operate without cloggin r."

by stringy material as it passes through the mill.

What I claim and desire to secure by Letters Patent is:

1. A screen for hammer and like mills including laterally spaced arcuate rails having a curvature adapted to substantially correspond with curvature of the rotor chamber in which the screen is to used, bars connecting ends of the rails to provide a frame adapted for insertion over the discharge opening of the mill, and substantially flat blades projecting from the rails inwardly of the frame with the blades on one rail staggered with respect to the blades on the other rail to provide a tortuous passageway, each of said blades haying oppositely disposed cutting edges converging toward the opposite rail with the cutting edges of the blades on one rail facing the cutting edges of the blades on the opposite rail to provide cutting edges at both sides of the portions of said passageway therebetween.

2. A screen for hammer and like mills including laterally spaced arcuate rails having a curvature adapted to substantially correspond with curvature of the rotor chamber in which the screen is to be used, bars connecting ends of the rails to provide a frame adapted for insertion over the discharge opening of the mill, and substantially fiat blades projecting from the rails inwardly of the frame with the blades on one rail staggered with respect to the blades on the other rail to provide a tortuous passageway, each of said blades having oppositely disposed cutting edges converging toward the opposite rail with the cutting edges of the blades on one rail facing the cutting edges of the blades on the opposite rail to provide cutting edges at both sides of the portions of said passageway therebetween, said cutting edges being of a length to extend beyond the median point between the rails of said frame.

3. A screen for hammer mills including laterally spaced arcuate rails having a curvature adapted to substantially correspond with the curvature of the rotor chamber in which the screen is to be used, substantially flat triangular blades arranged in staggered relation on the respective rails to provide a tortuous passageway therebetween and having apertured base portions registering with apertured portions of the rails, fastening devices extending through said apertures to secure the blades, said blades having oppositely disposed cutting edges converging toward the opposite rail with the cutting edges of the blades on one rail facing the cutting edges of the blades on the opposite rail to provide cutting edges at both sides'of the portions of the passageway therebetween.

4. A screen for hammer mills including laterally spaced arcuate rails having a curvature adapted to substantially correspond with the curvature of the rotor chamber in which the screen is to be used, substantially fiat triangular blades arranged in staggered relation on the respective rails to provide a tortuous passageway therebetween and having apertured base portions registering with apertured portions of the rails, fastening devices extending through said apertures to secure the blades, said blades having oppositely disposed cutting edges converging toward the opposite rail with the cutting edges of the blades on one rail facing the cutting edges of the blades on the opposite rail to provide cutting edges at both sides of the portions of the passageway therebetween, said blades being of a size relatively to the spacing of the rails whereby the apex formed by the oppositely disposed cutting edge of one blade extends beyond the median point between said rails.

FARRELL G. LIVELY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 153,429 English July 28, 1874 792,485 Williams June 13, 1905 953,111 Williams Mar. 29, 1910 1,170,389 Armstrong Feb. 1, 1916 1,821,912 Pfeiffer Sept. 1, 1931 2,066,621 Gray Jan. 5, 1987 2,386,021 Wetmore Oct. 2, 1945 

